1. Field of the Invention
The present invention is directed to a multistage radial compressor for compressing in particular gaseous fluids.
2. Description of the Related Art
The compressor of the present invention includes a housing in which a flow channel is formed for the fluid to be compressed, an impeller with a plurality of impeller vanes which are arranged in the flow channel and are rotatable with the impeller around a driveshaft, and 3D return blading with a plurality of return vanes which are fixed with respect to rotation relative to the compressor housing. The flow channel has a curved deflecting channel which is arranged in front of the return vanes in the flow direction.
A radial compressor of the type mentioned above is known, for example, from DE 42 34 739 C1 corresponding to U.S. Pat. No. 5,490,760, DE 196 54 840 A1, DE 34 30 307 A1 corresponding to U.S. Pat. No. 4,579,509, and DE 195 54 840 A1.
Particularly at higher volume flows, the flow angle distribution at the entrance of a 180-degree bend between two stages of the compressor is very uneven as a result of the impeller outlet flow, which leads to severe faulty inlet flows in the previously known 2D return blading and, therefore, to unwanted flow losses. If the diffuser ratio is decreased in order to achieve smaller structural dimensions, the incident flow losses and secondary flow losses increase.
DE 195 02 808 C2 discloses a single-stage radial compressor having a stationary guide wheel or diffuser on the radial outer side of an impeller. The guide vanes of the diffuser have a twist along their length in the manner of a logarithmic spiral so that the guide vanes have inlet edges and outlet edges that are twisted relative to one another. Use of the diffuser as return blading to a subsequent vane with an inlet flow from a curved deflecting channel is not considered.